Intrusion detection equipment is intended to protect closed areas against intrusion to prevent vandalism and/or burglary. There are many types of intrusion detectors available at the present time which use different detection sensors. There are capacitor type detectors, there are sonic detectors, vibration detectors and acoustic intrusion detections, among others. Acoustic intrusion detectors analyse the surrounding noises in protected areas to detect any unusual patterns such as would be generated by intruders. All of the systems presently available suffer because of "false alarms" generated by inherent conditions and not by intruders.
There are no known intrusion detectors on the market which identify intrusions by analysing the pattern of the detected signal in the protected areas.
There are currently available security systems based on remotely controlled listening devices where noise analysis is done by the operator listening to the noise. However there are no analysis and decision circuits located within the detection equipment itself.
A major reason for the non-availability of detectors incorporating analysis and decision circuits is that it is believed by those skilled in the art that such detectors show a high false alarm fate due to random non-relevant noises. False alarms are a cause of low reliability and even gradual loss of sensitivity.
Available intrusion detector systems using acoustic detectors are an example of vulnerability to false alarms. Strong short duration noises such as engine "back-fire" or supersonic booms tend to trigger such detectors unless its sensitivity is set to be far below the sensitivity needed to detect an intrusion.